During the lifetime of a patient, it may be necessary to perform a total shoulder replacement procedure on the patient as a result of, for example, disease or trauma. In a total shoulder replacement procedure, a humeral prosthesis is used to replace the natural head of the patient's humerus. The humeral prosthesis typically includes an elongated stem component that is implanted into the intramedullary canal of the patient's humerus and a hemispherically-shaped prosthetic head component that is secured to the stem component. In such a total shoulder replacement procedure, the natural glenoid surface of the scapula is resurfaced or otherwise replaced with a glenoid component that provides a bearing surface upon which the prosthetic head component of the humeral prosthesis articulates.
However, in some cases the patient's natural shoulder, including its soft tissue, has degenerated to a severe degree of joint instability and pain. In many such cases, it may be necessary to change the mechanics of the shoulder. Reverse shoulder implants are used to do so. As its name suggests, a reverse shoulder implant reverses the anatomy, or structure, of the healthy shoulder. In particular, a reverse shoulder implant is designed such that the prosthetic head (i.e., the “ball” in the ball-and-socket joint) known as a glenosphere component is secured to the patient's scapula, with the corresponding concave bearing (i.e., the “socket” in the ball-and-socket joint) known as a humeral cup being secured to the patient's humerus. Such a reverse configuration allows the patient's deltoid muscle, which is one of the larger and stronger shoulder muscles, to raise the arm.
In some cases, the patient's natural shoulder anatomy has also suffered trauma such as a proximal humeral fracture. Proximal humeral fractures are one of the most common fractures among elderly patients. In a proximal humeral fracture, the patient's humerus generally breaks into a number of pieces including the humeral head, the greater tuberosity, the lessor tuberosity, and the humeral shaft.